The present invention relates generally to input/output drivers and more particularly to an input/output driver having multiple input/output buffers individually programmable to function as input or output drivers.
Input/output drivers are widely used in digital circuits to buffer input and output signals transmitted to and from different pans of a system and external devices. One type of prior an input/output (I/O) driver is a bus transceiver having multiple I/O drivers in a package and a single direction control line for all of the I/O drivers in the package. Individual direction control for the drivers is not provided. A 54AS645 bus transceiver manufactured by Texas Instruments, Inc. is an example of this type of I/O driver. Another type of prior an bus transceiver includes multiple I/O drivers in a single package and includes individual direction controls for each driver in the package. An external programming apparatus is required for programming of direction control. A 54LS449 bus transceiver manufactured by Texas Instruments, Inc. is an example of this type of I/O driver. A programmable array logic device (PAL) such as a PAL16L8 manufactured by Advanced Micro Devices is another type of prior an I/O driver. Multiple drivers are provided and the individual drivers can only programmed prior to installation of the device on a circuit card. Design changes require replacement of the device with a newly programmed PAL.
There exists a need for a programmable bidirectional input/output driver which can be used as a generic buffer in digital logic circuits and for a device with this capability that can be used in conjunction with programmable gate arrays to provide a genetic connector for use in digital logic circuits. This type of device enables system design modifications to be effected without the need to physically modify the circuitry.
An advantage of the invention is to provide a programmable bidirectional input/output driver. Another advantage of the invention is to provide a programmable bidirectional I/O driver that performs as a programmable connector between low current drive logic elements and high current drive systems. Yet another advantage of the invention is to provide an I/O driver that can be used in conjunction with programmable gate arrays to provide a genetic bidirectional input/output driver to replace existing but out-of-date input/output drivers. Still another advantage of the invention is to provide a programmable bidirectional I/O driver having multiple drivers that can be individually programmed in a daisy chain configuration. Another advantage of the invention is to provide a programmable I/O driver that can be logically reconfigured for direction without physical reconfiguration of the device. Yet another advantage of the invention is to provide a programmable bidirectional I/O driver that can be reconfigured after assembly upon a reset command.